Production of Sheet Bimetal

Περίληψη:

Multilayer material is obtained by joining different metals producing a range of different good properties of the constituent metals in the obtained material, like:
- good structural properties of one constituent metal, and good corrosion resistance, shearing and sliding properties or abrasive hardness of the other constituent metal, and
- good conductivity of one metal, and good heat resistance of the other constituent metal.
It should be noted that price of the article made of multilayer material becomes quite low due to substitution, even up to 90%, of high grade alloys and scarce materials with cheap structural steel.

Multilayer material is obtained by joining different metals producing a range of different good properties of the constituent
metals in the obtained material, like:

good structural properties of one constituent metal,

good anticorrosive property, shearing and sliding properties or abrasive hardness of the other constituent metal,

good conductivity of one metal, and

good heat resistance of the other constituent metal.

It should be noted that price of the article made of multilayer material becomes quite low due to substitution, even up to 90%,
of high grade alloys and scarce materials with cheap structural steel.

Low Carbon Steel – Stainless Steel

Bimetal in this particular combination, absolutely substitutes stainless steel in all types of steel structures, securing
absolute corrosion resistance in the aggressive environments and very high toughness of the structure at the same time,
the quality that stainless steel it self does not possess.

Selection of the basic layer of a bimetal depends on the following working conditions of the equipment made of that specific
bimetal: temperature, working pressure and impact load. In most cases carbon and low-carbon steel with high yield points and
steels resistant to ageing and so called "creeping deformation" are used as the basic layers of this kind of bimetal.

The secondary layer, i.e., the adherent layer secures high resistance to corrosion in the aggressive ambient and frequently
chrome-nickel (Cr-Ni) steels are used as the adherent layers.

Technological character of bimetal considerably widens the scope of use of stainless steel in different industries.
In comparison to stainless steel, bimetal is more successfully used in the construction of: reservoirs, tanks for aggressive
liquids and gases, heat exchangers, digesters, mixers, agitators, hydroelectric power stations (turbine blades) dam gates,
pipeline components, steam pipeline components, steam separators and many others.

Carbon Steel – Titanium

With the development of processing and chemical industry, high alloy Cr-Ni steels proved to be not enough resistant in
many cases. Advantage of titanium over other anticorrosive metals is that when titanium corrodes, corrosion does not take
place at some individual area or areas of the metal but uniformly over the whole area of the metal. Pitting or intracrystal
corrosion is a very rare case.

Titanium its alloys in combination with structural steel, besides securing high anticorrosive resistance in an aggressive
ambient, considerably improve the structure of the equipment working in acid-baths, like, hydrochloric acid, sulphuric acid
and sodium chloride.

Steel Sheet Joined to Copper Sheet or Tombac (CuZn10)

The bimetal obtained by combining copper or brass with steel has a wide range of application in industry.

Three-layer bimetal strips are of special interest, they are used for making ammunition. These bimetal strips are also
used in the automobile industry for production of cooling radiators, reservoirs and gaskets for motor-heads.

Bimetal Industrial Cutters

Bimetal cutters, compared to cutters made of uniform steel only, have many technical, technological and economic advantages.
Firstly, in bimetal 90% cheaper structural steel substitutes for expensive tool steel and high speed steel.

In the case of bimetal only the cutting edge of a tool is made of quality steel. Use of bimetal makes the heat treatment,
straightening, grinding and sharpening processes easier and similar.

In the event of bimetal cutters the possibility of burning of cutting edge during hardening is excluded because the heat
is intensively transferred to the structural steel side. Hardness of the cutting edge of a cutter of this kind is high and
so is the necessary toughness of the body made of structural steel. That is why they are absolutely safe for exploitation
and safe even when they are in direct contact with any worker. These cutters are used in industries, like: paper, metal,
wood, textile and similar.

Bimetal Sliding Bearing (Steel-AlSn20Cu)

A bimetal bearing comprises of a steel shell with high modules of elasticity, shell which makes a rigid bearing assembly,
and a layer of the alloy used which makes the inside wall of the bearing. The hard components are capable of bearing shocks
or impacts without causing any deformation while the soft base (plays the role of a shock absorber) absorbs those impacts
or shocks and adapts to the journal.

Sliding bearing alloy has the following characteristics: ability of surface adaptation, ability of adhering to oil layer,
small coefficient of expansion, good thermal conductivity, good resistance to corrosion in fatty medium and less sensitive
to deformation at edge. These bearings are mounted to diesel motors of locomotives, ships, to compressors, aggregates,
cranes, heavy vehicles and similar.

Bimetal Kitchen Utensils

Multilayer materials have bright prospects in manufacturing metal kitchen utensils because they have considerably higher
thermo-mechanical properties compared to those properties of single-layer materials.

Manufacturing of bimetal kitchen utensils differs from the manufacturing of present generation metal kitchen utensils
only in deep drawing of bimetal straight into utensils without any subsequent welding of heavy thermo-bottoms. By bimetal
kitchenware has a very artistic look, its inside is made of 18/10 stainless steel while the outside is made of a
high-polished copper or brass layer.

Heat Exchangers

Heat exchangers, particularly tubular heat exchangers are very frequent components of equipment used in processing industry.
Generally, most of these heat exchangers are in direct contact with aggressive mediums during exploitation, so it is
essential that their parts are made of stainless steel or titanium. Due to heavy consumption of high alloy and scarce
materials, it is economic that massive heat exchangers are made of bimetal.

In the case of tubular exchangers, welding of pipes to the pipe wall of exchangers is a bottle-neck in the manufacturing
process. Technology of welding by explosion energy secures absolute homogeneity of the joint, because it creates a genuine
metallic connection between the pipe and the pipe wall of the exchanger where toughness of the joint is higher than toughness
of the weaker metal.

Welding of metal by explosion energy is widely used for manufacturing different types of panel or plate heat exchangers also.
Cooling ducts are cut on a steel plate first, over which a thin plate layer of stainless steel or copper is built-up (welded).
Deformation of ducts during exploitation itself is negligible because they cool intensively during exploitation. Repairing
of heat exchangers (due to wear of the thin plate of stainless steel or copper during exploitation) heads to welding of a
new plate by explosion energy.

Electro Contacts

Bimetal Steel-Aluminum serves as the intermediate joint of steel and aluminum in the structures for obtaining aluminum.
Today bimetal, obtained using explosion energy, is the only dependable solution for electrolysis of clay, because use
of this type of bimetal reduces electrical resistance of the contact even five times and extends the exploitation time more
than double compared to these factors of bimetals obtained with other technologies of joining aluminum and steel.

Trimetal Sheet (Steel-Al-Alma4.5) for Shipbuilding

Aluminum and its alloys have a very bright future in making different structures which are exposed to sea or salt water ambient.
Lately aluminum alloys are more and more used as structural material in shipbuilding where the lower construction or hull of a
ship is made of steel but the inside metal sheet of hull is aluminum.

This type of construction considerably increases the carrying capacity of a ship and its maneuvering capability. It is of
particular importance that the navigation system of a ship is located in an antimagnetic field.